Forty-one percent of American adults consume calorie-free sweeteners like Splenda, Equal, and stevia on a daily basis. That’s a real problem since we really have no idea what these faux sugars are doing to our bodies—even stevia, which is plant-based, not lab-created like the others. Many people believe these sweeteners can help with weight loss, but more and more research suggests the exact opposite is true.
The latest takedown of low-calorie sweeteners comes from a sweeping new meta-analysis published in the Canadian Medical Association Journal. After analyzing 37 studies involving more than 400,000 people, researchers found zero proof that they help people drop pounds. However, they found plenty of evidence linking artificial sweeteners to weight gain. In fact, over time, those who drank just one diet beverage a day had an elevated of risk of obesity, heart disease, and type 2 diabetes.
“People generally consume nonnutritive sweeteners believing they are a healthy choice, but we do not know if they are a truly harmless alternative to sugar,” says lead researcher Meghan Azad, assistant professor of pediatrics and child health at the University of Manitoba. “Based on all of the research done so far, there is no clear evidence of a long-term benefit, but there is evidence of potential adverse effects from long-term consumption.”
Although experts still don’t know exactly how low-calorie sweeteners influence weight gain, many suspect our bodies just don’t know how to handle these substances. “Studies suggest that when given something sweet that doesn’t have calories, the body doesn’t respond properly,” Azad says. “It is used to saying, ‘here’s sugar, so here are calories’ and responding in a certain way.” This bait-and-switch might reprogram metabolic pathways, eventually leading to weight gain, high blood sugar, and insulin resistance, she adds.
Additionally, artificial sweeteners disrupt the gut microbiome, which could also spell trouble. “We know that gut bacteria partially determine how much energy we absorb from food, and research has shown that certain combinations of gut bacteria promote excess weight gain,” Azad explains. “Routinely consuming artificial sweeteners may be selecting for an ‘obesogenic’ microbiome.”
This research review differed from most investigations of low-calorie sweeteners in an interesting way: It included research on stevia. Since stevia is a newer sweetener choice, far fewer studies have looked into it than, say, Splenda or Equal. And because of that, it’s tough to draw many solid conclusions about stevia’s long-term cardiometabolic health effects. Still, Azad believes there’s enough reason to be cautious.
“There’s a perception that because stevia is natural it is therefore healthier,” she says. “That may or may not be true, but we don’t have the evidence to say. If the issue with nonnutritive sweeteners is their effect on microbiome, maybe stevia affects gut microbes in a different way. But if the issue is the sweet taste affecting metabolic pathways, then it may not matter what the source of the low-calorie sweetener is. The jury is still out.”
Until we know more about sugar substitutes’ long-range impacts, “check your habit,” says Azad. “Consuming sugar substitutes as everyday routine, which most people who use them do, is probably not the best choice.”